Multiple sclerosis (abbreviated MS), is an autoimmune condition in which the immune system attacks the central nervous system, leading to demyelination. Disease onset usually occurs in young adults, and it is more common in females. It has a prevalence that ranges between 2 and 150 per 100,000.
MS affects the ability of nerve cells in the brain and spinal cord to communicate with each other. Nerve cells communicate by sending electrical signals called action potentials down long fibers called axons, which are wrapped in an insulating substance called myelin. In MS, the body's own immune system attacks and damages the myelin. When myelin is lost, the axons can no longer effectively conduct signals. The name multiple sclerosis refers to scars (scleroses—better known as plaques or lesions) in the white matter of the brain and spinal cord, which is mainly composed of myelin. Although much is known about the mechanisms involved in the disease process, the cause remains unknown. Theories include genetics and/or infections. Different environmental risk factors have also been found.
Almost any neurological symptom can appear with the disease, and often progresses to physical and cognitive disability. MS takes several forms, with new symptoms occurring either in discrete attacks (relapsing forms) or slowly accumulating over time (progressive forms). Between attacks, symptoms may go away completely, but permanent neurological problems often occur, especially as the disease advances. MS is sometimes incidentally identified during neurological examinations performed for other causes.
There is no known cure for MS. Treatments attempt to return function after an attack, prevent new attacks, and prevent disability. MS medications can have adverse effects or be poorly tolerated, and many patients pursue alternative treatments, despite the lack of supporting scientific study. The prognosis is difficult to predict; it depends on the subtype of the disease, the individual patient's disease characteristics, the initial symptoms and the degree of disability the person experiences as time advances.
The life expectancy of people with MS, at least for earlier years, is nearly the same as that of unaffected people. Almost 40% of patients reach the seventh decade of life. Nevertheless, half of the deaths in people with MS are directly related to the consequences of the disease, while 15% more are due to suicide, a percentage much higher than in the healthy population.
Although most patients lose the ability to walk prior to death, 90% are still capable of independent walking at 10 years from onset, and 75% at 15 years.
MS results in a thinning or complete loss of myelin and, as the disease advances, the cutting (transection) of the neuron's extensions or axons. When the myelin is lost, a neuron can no longer effectively conduct electrical signals. A repair process, called remyelination, takes place in early phases of the disease, but the oligodendrocytes cannot completely rebuild the cell's myelin sheath. Repeated attacks lead to successively fewer effective remyelinations, until a scar-like plaque is built up around the damaged axons.
Apart from demyelination, which is caused by T cells, the other pathologic hallmark of the disease is inflammation. The central involvement of a wide range of inflammatory mediators in progressive multiple sclerosis is well established. These factors play multiple roles including facilitating T cell migration into the central nervous system (CNS), break down of blood-brain barrier and promotion of myelin destruction and axon degeneration in the early phase of disease. The later phase is associated with predominantly neuroaxonial damage as a result naked axon exposure in demyelinated plaques.
Treatment
Although there is no known cure for multiple sclerosis, several therapies have proven helpful. The primary aims of therapy are returning function after an attack, preventing new attacks, and preventing disability. As with any medical treatment, medications used in the management of MS have several adverse effects. Alternative treatments are pursued by some patients, despite the shortage of supporting, comparable, replicated scientific study.
Current treatment strategies involve both immunomodulating as well as immunosuppressive strategies which are aimed at reducing the inflammatory phase. During symptomatic attacks, administration of high doses of intravenous corticosteroids, such as methylprednisolone, is the routine therapy for acute relapses. The aim of this kind of treatment is to end the attack sooner and leave fewer lasting deficits in the patient. Although generally effective in the short term for relieving symptoms, corticosteroid treatments do not appear to have a significant impact on long-term recovery. Potential side effects include osteoporosis and impaired memory, the latter being reversible.
Disease-modifying treatments are expensive and most of these require frequent (up-to-daily) injections. Others require IV infusions at 1-3 month intervals. Non-specific agents such as interferons have limited long term efficacy and are not well tolerated.
As of 2007, six disease-modifying treatments have been approved by regulatory agencies of different countries for MS. Three are interferons: two formulations of interferon beta-1a (trade names Avonex, CinnoVex, ReciGen and Rebif) and one of interferon beta-1b (U.S. trade name Betaseron, in Europe and Japan Betaferon). A fourth medication is glatiramer acetate (Copaxone). The fifth medication, mitoxantrone, is an immunosuppressant also used in cancer chemotherapy, approved only in the USA and largely for secondary progressive MS. The sixth is natalizumab (marketed as Tysabri), an anti-VLA-4 antibody which blocks immune cell trafficking and effectively reduce CNS inflammation. All six medications are modestly effective at decreasing the number of attacks and slowing progression to disability, although their efficacy rates differ, and studies of their long-term effects are still lacking. Comparisons between immunomodulators (all but mitoxantrone) show that the most effective is natalizumab, both in terms of relapse rate reduction and halting disability progression; it has also been shown to reduce the severity of MS. Mitoxantrone may be the most effective of them all; however, it is generally not considered as a long-term therapy, as its use is limited by severe cardiotoxicity.
The interferons and glatiramer acetate are delivered by frequent injections, varying from once-per-day for glatiramer acetate to once-per-week (but intra-muscular) for Avonex. Natalizumab and mitoxantrone are given by IV infusion at monthly intervals. Treatment of progressive MS is more difficult than relapsing-remitting MS. Mitoxantrone has shown positive effects in patients with secondary progressive and progressive relapsing courses. It is moderately effective in reducing the progression of the disease and the frequency of relapses in patients in short-term follow-up. No treatment has been proven to modify the course of primary progressive MS.
A number of treatments that may curtail attacks or improve function are under investigation. Some of these treatments involve the combination of drugs that are already in use for multiple sclerosis, such as the joint administration of mitoxantrone and glatiramer acetate (Copaxone). However, most treatments already in clinical trials involve drugs that are used in other diseases. Most recently, auto-antibodies reactive with neurofascin 186, a principle nerve fibre protein, have been strongly implicated in neuronal degeneration associated with progressive MS, and represent a potential new target.
As with any medical treatment, these treatments have several adverse effects. One of the most common is irritation at the injection site for glatiramer acetate and the interferon treatments. Over time, a visible dent at the injection site, due to the local destruction of fat tissue, known as lipoatrophy, may develop. Interferons produce symptoms similar to influenza; some patients taking glatiramer experience a post-injection reaction manifested by flushing, chest tightness, heart palpitations, breathlessness, and anxiety, which usually lasts less than thirty minutes. More dangerous are liver damage from interferons and mitoxantrone, the immunosuppressive effects and cardiac toxicity of the latter; and the putative link between natalizumab and some cases of life-threatening complications such as progressive multifocal leukoencephalopathy.
Therefore there is still a need for alternative MS treatments which have improved therapeutic and side-effect profiles.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art therapies or provide a useful alternative.